This proposal involves the study of NADPH-cytochrome c reductase and its role in the electron transport systems concerned with mixed function oxidation of drugs, carcinogens, steroids, and fatty acids. Experimental goals include 1) the study of w-hydroxylation of fatty acids in liver and kidney cortex microsomes to determine the pathway of electron transfer from NADPH and/or NADH; 2) the study of methemoglobin reduction in human erythrocytes to characterize the additional cofactor required for methemoglobin reduction by methemoglobin reductase and cytochrome b5 and to determine the reaction stoichiometry; 3) to determine the cellular and sub-cellular localization of NADPH-cytochrome c reductase and cytchrome b5 in various organs by fluorescein-antibody and ferritin-antibody labelling techniques using conventional and electron microscopy; 4) to pursue the purification of NADPH-cytochrome c reductase by detergent methods in order to obtain a homogeneous preparation which will interact with various purified cytochrome P450 preparations; and 5) the study of the mechanism of protease- and detergent-solubilized NADPH-cytochrome c reductase with respect to artificial and physiological electron acceptors.